#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(?<=atitle=).*?(?=&)"
Local $sString = "ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rfr_id=info%3Asid%2Focoins.info%3Agenerator&rft.genre=article&rft.atitle=Parliamentarism Rationalized&rft.title=East European Constitutional Review&rft.stitle=E. Eur. Const. Rev.&rft.date=1993&rft.volume=2&rft.spage=33&rft.au=Tanchev, Evgeni&rft_id=http://heinonline.org/HOL/Page?handle%3Dhein.journals/eeurcr2%26id%3D33%26div%3D%26collection%3D" & @CRLF & _
""
Local $sSubst = ""
Local $sResult = StringRegExpReplace($sString, $sRegex, $sSubst)
MsgBox($MB_SYSTEMMODAL, "Result", $sResult)
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for AutoIt, please visit: https://www.autoitscript.com/autoit3/docs/functions/StringRegExp.htm